After screening and eligibility assessment, patients were randomized (in a 1:1 ratio) to receive either clofarabine or matching placebo, in addition to cytarabine. Randomization was stratified by remission status following the first induction regimen (CR1): no remission [i.e., CR1 = refractory] or remission <6 months vs remission ≥6 months. During randomization by interactive voice response system (IVRS), there were 10 participants misclassified to the CR1 <6 months stratum and 12 participants misclassified to CR1 ≥6 months stratum. The error did not affect the participants' treatment, only the stratification. Due to the misclassification, outcomes that used strata in their analysis were analyzed twice: once with the 'randomized stratification' which includes the misclassification and once with the 'calculated stratification' in which participants appear in the 'correct' strata.